diff --git a/build.xml b/build.xml
index 27a1ea40..ab0a0be4 100644
--- a/build.xml
+++ b/build.xml
@@ -1,12 +1,10 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE project [
-       <!ENTITY add-proguard-release SYSTEM "add-proguard-release.xml">
-]>
 <project name="Orbot" default="help">
+
     <!-- The local.properties file is created and updated by the 'android' tool.
          It contains the path to the SDK. It should *NOT* be checked into
          Version Control Systems. -->
-    <loadproperties srcFile="local.properties" />
+    <property file="local.properties" />
 
     <!-- The ant.properties file can be created by you. It is only edited by the
          'android' tool to add properties to it.
@@ -43,25 +41,23 @@
 
     <!-- quick check on sdk.dir -->
     <fail
-            message="sdk.dir is missing. Make sure to generate local.properties using 'android update project'"
+            message="sdk.dir is missing. Make sure to generate local.properties using 'android update project' or to inject it through an env var"
             unless="sdk.dir"
     />
 
-
-<!-- extension targets. Uncomment the ones where you want to do custom work
-     in between standard targets -->
-<!--
-    <target name="-pre-build">
-    </target>
-    <target name="-pre-compile">
-    </target>
-
-    /* This is typically used for code obfuscation.
-       Compiled code location: ${out.classes.absolute.dir}
-       If this is not done in place, override ${out.dex.input.absolute.dir} */
-    <target name="-post-compile">
-    </target>
--->
+    <!--
+        Import per project custom build rules if present at the root of the project.
+        This is the place to put custom intermediary targets such as:
+            -pre-build
+            -pre-compile
+            -post-compile (This is typically used for code obfuscation.
+                           Compiled code location: ${out.classes.absolute.dir}
+                           If this is not done in place, override ${out.dex.input.absolute.dir})
+            -post-package
+            -post-build
+            -pre-clean
+    -->
+    <import file="custom_rules.xml" optional="true" />
 
     <!-- Import the actual build file.
 
@@ -84,5 +80,4 @@
     <!-- version-tag: 1 -->
     <import file="${sdk.dir}/tools/ant/build.xml" />
 
-&add-proguard-release;
 </project>